Task Group 90
Age-dependent Dose Conversion Coefficients for External Exposures to Environmental Sources

A Task Group under Committee 2

External exposure to environmental sources is an important pathway of exposure of the public after major releases of radionuclides to the environment. In the early stage after a nuclear accident, internal exposures due to inhalation and ingestion of radionuclides are likely to significantly contribute to organ doses and effective dose. However, some time after an accidental release external exposure is a major contributor to the doses of members of the public. This is also the case after the accident at the nuclear power plant (NPP) in Fukushima Prefecture, Japan in March 2011. Age-dependent dose coefficients for the internal exposures have been evaluated comprehensively by ICRP (Publications 56, 67, 69, 71, 72 currently under revision), while age-dependent dose conversion coefficients for external exposures have not been evaluated by ICRP. The purpose of the proposed report is, therefore, to provide age-dependent dose conversion coefficients for external environmental exposures.

Conversion coefficients are needed to evaluate effective dose from measurements of air kerma, the absorbed dose in air, or the ambient dose equivalent. Calculation of the conversion coefficients requires the evaluation of the environmental field (i.e. density and composition of soil, radionuclide distribution), the model of the human body, i.e. the phantoms that represent the members of the public, and the simulation of the radiation transport. Organ doses depend on body mass since, in external photon exposure, increasing amounts of overlying tissue enhances the shielding of the organs located beneath the subcutaneous adipose mass. Therefore, reference models of adults as well as of children of different ages will be used in the calculations.

Conversion coefficients for environmental exposures will be computed for the ICRP voxel-based adult male and female reference computational phantoms (ICRP Publication 110) as well as for the 10 pediatric NURB-based phantoms of the University of Florida. The latter have been selected to become the reference ICRP pediatric phantoms. The Task Group (TG) will identify the most probable exposure scenarios for the simulation (see outline of the task). The TG will have close collaboration with DOCAL.

Symposium on Radiological Protection Dosimetry 18 Feb 2016

Nina Petoussi-Henss (Chair), Helmholtz Zentrum Mnchen, Germany
Michael Bellamy (Member), Oak Ridge National Laboratory, USA
Wesley E. Bolch (Member), University of Florida, USA
Keith Eckerman (Member), Oak Ridge National Laboratory (ORNL), USA
Akira Endo (Member), Japan Atomic Energy Agency (JAEA), JAPAN
Nolan E. Hertel (Member), Georgia Institute of Technology, USA
John G.S Hunt (Member), The Instituto de Radioproteo e Dosimetria, Brazil
Jan T.M. Jansen (Member), Public Health England, UNITED KINGDOM
Choonsik Lee (Member), National Cancer Institute, USA
Kimiaki Saito (Member), Japan Atomic Engergy Agency, Japan
Daiki Satoh (Member), Japan Atomic Engergy Agency, Japan
Helmut Schlattl (Member), Bundesamt fr Strahlenschutz, GERMANY
Yeon Soo Yeom (Member), National Cancer Institute, USA
Song Jae Yoo (Member), Korea Institute of Nuclear Safety(KINS), Korea